Influência do detalhamento dos estribos na resistência à punção de lajes lisas de concreto armado

Abstract

Stirrups used as punching shear reinforcement in reinforced concrete flat slabs can provide strength gains to the regions of slab-column connection. To this end, the standards recommend that the details should be made in order to ensure their anchorage in the flexural reinforcement bars, involving them. However, designs that strictly follow the detailing criteria may become difficult to execute, or even unfeasible, due to the concentration of longitudinal bars in these regions. The need for more practicality in the assembly of stirrups has driven the development of reinforcement systems, whose anchorage details are not yet contemplated in the normative prescriptions. Therefore, the scientific validation of such constructive alternatives is necessary. In this context, this work seeks to contribute to the validation process of numerous constructive alternatives for stirrups used as punching shear reinforcement, so that, in this way, they can be properly disseminated in the technical environment. The objective of this work is to evaluate the influence of the variation of the stirrups anchorage on its efficiency, from an extensive review of scientific literature, which enabled the assembly of a database containing 119 punching shear tests in internal slab-column connections, subjected to symmetric loading. The analysis parameters were the increments of strength provided as a function of the increase of force played by the shear reinforcement. At the end, the most efficient anchorage details for different types of stirrups used as punching shear reinforcement were defined and, for such stirrups, assembly instructions were proposed, aiming the optimization of the constructive process.